The present invention relates to microlithographic projection systems and more particularly to a reticle mount for use in a microlithographic projection system which permits the reticle to be precisely translated and rotated in its own plane.
As is understood by those skilled in the manufacture of integrated circuits, the fabrication of such devices requires the forming, on the surface of a semiconductor wafer, of a succession of complex images which must be overlaid one on top of the other in precise registration. Thus, in the microlithographic projection systems which are employed for forming these images, some mechanism must be provided for precisely positioning the reticle with respect to the wafer or vice versa. In most microlithographic projection systems manufactured and sold heretofore, the reticle is typically aligned mechanically on its mount at the object plane of the optical column and fine adjustment is provided by translating or rotating the wafer to effect precise registration, registration being sensed by optical systems which align fiducial marks on the wafer with corresponding marks on the reticle or the frame holding the reticle. As will be understood, however, it is relative motion between the reticle and the wafer which is significant and either element may be moved to effect alignment.
Among the several objects of the present invention may be noted the provision of a novel mount for a microlithographic reticle permitting precise lateral and rotational movement of the reticle within its own plane; the provision of such a mount which permits such movement without hysteresis; the provision of such a mount which strongly resists movements other than in the plane of the reticle; the provision of such a mount which facilitates precise positioning; the provision of such a mount which is highly reliable and which is of relatively simple and inexpensive construction. Other objects and features will in part be apparent and in part pointed out hereinafter.